a) Field of the Invention
The present invention is directed to an arrangement and method for automatic positioning of the device with respect to the patient's eye to be examined in the x, y and/or z coordinates. This method can advantageously be used to facilitate the determination of biometric data of the eye and other adjustments relating to diagnostics and therapy based on manual or stored method sequences. Data from an examination can be stored in order to examine the corresponding regions in another, subsequent examination under the same conditions so that changes can be determined.
b) Description of the Related Art
Technical solutions in which an ophthalmologic device is positioned semi-automatically or fully automatically on the eye to be examined after detection of the eye are already known from the prior art.
Patent EP 1 088 511 describes an ophthalmologic device which has a positioning unit for orientation of the measuring unit with respect to the eye to be examined. For this purpose, a detection unit which determines the relative position of the measurement unit with respect to the eye and monitors this position during measurement is provided. The determined measurement values are stored or rejected depending on the eye position determined by the detection unit. In this way, only measurements that were recorded when the eye was accurately positioned are processed and stored. This solution is disadvantageous compared with the method suggested in the present application due to the fact that the measurement unit of the ophthalmologic device must be roughly oriented by the user by means of a joystick at the start of the examination, i.e., when the patient sits in front of the device and the patient's eye has been brought into a fixed position. The detection unit cannot determine the position of the eye and send the corresponding signals to the positioning unit for fine adjustment until after this rough adjustment. In other words, the process is subject to subjective influences such as the experience of the user in adjusting.
An automatically aligning optometric measurement device and the method for its use are described in U.S. Pat. No. 6,145,990. This solution has means for projecting a light mark on the eye, means for evaluating corneal reflex images, and means for controlling the actuating drives for exact positioning of the optometric measurement device. Positioning is carried out in all three coordinate directions for the first eye and then for the second eye based on the position of two light marks relative to one another, these light marks being generated from the corneal reflex image. After positioning, the corresponding measurements are carried out on the eye. Depending on whether or not the measurement is successfully carried out, a new measurement is carried out or the device is positioned on the other eye.
In the solution described in U.S. Pat. No. 6,220,706, the position of the eyes is likewise determined by illuminating the eyes and subsequently evaluating the reflected beam. For this purpose, two pairs of radiation emitter-photodetectors are arranged lateral to the eye in such a way that a radiation emitter and a photodetector of different pairs are located on each side of the eye. The photodetectors receive the radiation that is emitted by the respective associated radiation emitter and reflected by the eye. A controller analyzes the data of the photodetectors, which are constructed as 4-quadrant photodetectors, in order to determine the exact position of the eye. This technical solution determines, in particular, the focus position, i.e., the exact distance of the eye from the optics of the device.
The known technical solutions have the disadvantage that exact alignment of the measurement device to the eye either depends subjectively upon the user in the absence of automatic positioning or that additional technical devices are always required when automatic positioning is provided, which makes the overall device substantially more complicated and harder to oversee.